The working principle and application of temperature control valve
**Abstract:**
Thermostatic valves are essential components in heating systems, serving as the primary devices for regulating water flow and ensuring accurate temperature control. Without thermostatic valves, a heating system cannot be considered a metered and chargeable system. This paper provides an in-depth analysis of the structure and working principle of thermostatic valves. It explores the flow characteristics of these valves and how they interact with radiator performance and valve authority. By integrating these factors, the paper explains how thermostatic valves contribute to efficient thermal regulation. Additionally, it outlines the installation plan for temperature control valves and highlights their energy-saving benefits.
**Keywords:** Thermostatic valve, flow characteristics, valve authority, heat metering, radiator, temperature control
1. **Structure and Working Principle of Radiator Thermostatic Valve**
The user’s temperature control is achieved through the use of a radiator thermostatic control valve. This device consists of a thermostat controller, a flow control valve, and connecting parts. The thermostat is the core component, acting as a sensor that detects ambient temperature changes. When the temperature fluctuates, the temperature-sensitive element expands or contracts, causing the valve plug to move and adjust the water flow to the radiator. This, in turn, controls the heat output. The set temperature can be manually adjusted, and the valve automatically regulates the flow based on the desired indoor temperature, ensuring comfort and efficiency.
2. **Flow Characteristics and Regulation of Radiator Systems**
The adjustment performance of a radiator is influenced by three key factors: its thermal characteristics, the flow characteristics of the thermostatic valve, and the valve authority. The relative flow (G/Gmax) refers to the ratio of actual flow to maximum flow at a given valve opening. Similarly, the relative travel (l) represents the ratio of the valve stem position to its full stroke. The relationship between relative travel and relative flow is known as the flow characteristic curve, expressed as G/Gmax = f(l). Common types include linear, quick-opening, equal percentage, and parabolic characteristics.
For radiators, the heat output versus flow rate relationship typically follows a non-linear curve. As flow increases, heat dissipation tends to level off due to saturation. To ensure stable and responsive regulation, it is common to use valves with equal percentage flow characteristics, which counteract the inherent non-linearity of radiators.
3. **Impact of Valve Authority on System Regulation**
Valve authority plays a critical role in determining the adjustable range of a thermostatic valve. The adjustable ratio R is defined as the ratio of maximum flow (Gmax) to minimum flow (Gmin) that the valve can manage: R = Gmax / Gmin. In a radiator system, where the valve and radiator are connected in series, the adjustable ratio is directly related to the valve’s authority. For example, if a radiator has a flow capacity of 5 m³/h and the thermostatic valve has a valve authority of 88%, the effective adjustable ratio may be around 28, covering a flow range from 100% to 4%. The actual adjustable range varies depending on the temperature difference between the inlet and outlet of the radiator, as shown in the table below.
**Import and Export Temperature Difference (℃)** | **Adjustable Flow Range (%)**
--- | ---
5 | 100–6%
10 | 100–10%
15 | 100–15%
20 | 100–20%
By properly selecting and installing thermostatic valves, heating systems can achieve optimal thermal performance and energy efficiency, making them a crucial part of modern heating solutions.
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